托甫台地区TP327井区一间房组Q各向异性分析

碳酸盐岩储层中,裂缝和溶洞为主要储集空间,同时裂缝也是油气运移的主要通道,因此识别裂缝系统对于碳酸盐岩储层的评价尤为重要。以塔里木盆地托甫台地区TP327井区中奥陶统一间房组为研究对象,通过分析环状VSP数据的Q各向异性,描述了裂缝的发育情况。针对VSP井中检波器在目的层之上的情况,提出了一种将叠前初至波和反射波相结合的Q值估算方法。主要技术流程包括:①采用噪声压制方法消除反射波的虚假高频;②利用合成记录的标定,识别VSP单炮记录中的一间房组反射波;③基于Q各向异性特征,通过椭圆拟合分析区域裂缝发育的主方位和Q各向异性程度。该方法的应用结果表明,托甫台地区TP327井区一间房组裂缝发育的主方位为北东(NE)向,这与该区域较广泛发育的北东南西(NE-SW)向断裂的方向一致,从而验证了所提出的Q各向异性分析方法的可靠性和有效性。

Q-anisotropy analysis of the Yijianfang Formation in the TP327 well area of Tuofutai,China

In the Tarim Basin,cavern and fractures are the main carbonate reservoir spaces,with the latter also serving as the main channels for oil and gas migration.Therefore,the study of the fracture network is particularly important for the evaluation of these reservoirs.In this study,taking the Ordovician Yijianfang group in the Tofutai TP327 area of the Tarim Basin as a case study,the development of fractures was predicted through a Q-anisotropy analysis using Walkaround vertical seismic profile(VSP)data.For the geophones installed in wells that did not reach the target formation,the Q values of the latter were estimated using pre-stack VSP first arrivals and reflections.The following data processing methods were adopted:first,the false high frequency of the reflected wave was eliminated by noise suppression;then,the reflections of the Yijianfang group in VSP shot records were identified through calibration of the synthetic record;finally,the dominant fracture azimuth and Q-anisotropy of the Yijianfang group were predicted by ellipse-fitting the Q values.The results of the data processing identified NE as the dominant fracture azimuth,which is consistent with the widely developed NE–SW faults in the area,thereby confirming the effectiveness of the proposed Q-anisotropy analysis method.